It Started With a Cough
by coconut994777
Summary: Frisk comes down with a bad case of bronchitis, but Sans has his concerns. Post-Pacifist spoilers, Hurt/Comfort. Currently one-shot, will had more if requested!
1. Chapter 1

A/N- Inspired by a lot of the fanfics I have read over the past day or so, please comment if you'd like to see more Undertale fanfiction!

They had made a nice life for themselves above ground. Just outside where the barrier had been, Toriel opened a school for monster children and human children alike. With the help of kind, local humans, they worked together to ensure it was up to the standards of the regional schools. The monsters that emerged from the Underground built a small town around the entrance, with tourism and trade establishing the town rather quickly.

All of Frisk's friends made a living doing what they did best, and Frisk was very excited to be living with Toriel again. Alphys and Undyne moved in next door, and took in Papyrus as a roommate. Toriel invited Sans to live with her, and he promised to help out around the house while she managed the school. The two of them had feelings for one another since they shared jokes through the door connecting the Ruins to Snowdin, but they took it slow with Toriel being so busy.

Frisk loved their new school, they were appointed as student ambassador to connect the humans and monsters within the school. It was hard at first, but all of the kids openly accepted one another quite easily. Toriel was the principal, and also did much administration work as far as curriculum and ordering supplies.

After a long Friday at school, Frisk came home to the smell of Sans's hot dogs cooked on the stove.

"Hi Sans!" They called from the living room.

"Hey kid! Once you are done with homework, we'll have dinner. Tori's not gonna be home until late, because of the staff meeting."

"I know," Frisk coughed. And then coughed a little bit more, trying to suppress it as much as possible.

Sans peeked his head into the living room, "you ok there, buddy?"

Frisk looked over at San, "I think so, it just feels like a bad tickle", they said. "Can I have some tea?"

Sans nodded. "Coming right up!"

Frisk cleared their throat a little and then took off their shoes and coat to get started on some history homework .Sans brought out some tea and hot dogs after a little while, and they fell asleep on the couch with the television quietly playing Mettaton reruns.

Late in the evening, Toriel arrived home from her meeting, and gently woke her loved ones to get them to bed. While helping Frisk up the stairs, she noticed they coughed a little bit, and frowned. She hoped they had not gotten sick at school.

She kissed Frisk goodnight with some tea on their nightstand, and then crept back downstairs to spend some time with Sans. "Thank you so much for taking care of Frisk, the meeting ran longer than we thought."

"It's no problem, there are leftovers in the fridge, they were _dog-gone_ good!" He said, winking at her.

She smiled faintly, "That sounds perfect", and then paused for a moment. Is Frisk feeling all right? They were coughing when I brought them to bed."

Sans, nodding knowingly, replied with a sigh "I think they must be getting down with something, doesn't seem too serious though. I'll keep an eye socket out through the night."

Toriel held his hands, "what would I do without you?" She kissed his cheekbone and went to bed, yawning. Sans turned the TV off and checked his phone to see what his brother was up to. He felt bad for Papyrus being a bit of a third wheel for Undyne and Dr. Alphys, but the two of them said they didn't mind for now.

Sans awoke with a bit of a start, hearing a noise coming from the bathroom. He started closing his eyes when he heard something again, this time recognizing what it was.

He walked up to the bathroom door, "knock knock."

A child's voice weakly said "who's there?"

"Ash"

"Ash who?

"Hey kid, are you catching a cold?" Sans laughed at his own silly joke. He heard Frisk come to the door, looking very tired. "Doing okay?"

"Yeah," they said, rubbing their tired eyes, "that cough won't leave me alone."

"Take a warm shower, Toriel said that makes most anybody feel better. Maybe it'll wash away that cough" He paused, "Not my best joke, but you get the idea."

"Okay, I'll be out in a minute."

Sans tip-toed back to the couch, checking the clock as he drifted asleep, _1:50_

Sans yawned awake to keep himself from falling asleep, but checked the clock again, _2:30_ He looked over, and there was still a light on in the bathroom.

He went over and knocked on the door, without announcing it verbally, and heard a loud series of coughs. He checked the door handle; it was unlocked, so he looked inside. There he saw Frisk, in their clothes, sitting up against the wall next to the shower. "Uh, buddy?"

Frisk looked up, "I thought the steam might help, but it is a little hard to breathe. I was gonna open the window but I'm too tired"

Sans picked them up and carried Frisk to their room, tucking them in gently so as not to trigger more coughing, and quietly closed the bedroom door. As soon as he did, he heard more coughing, and a wheezing sound. He opened the door quickly to find Frisk gasping for breath. "Hey, woah, what happened?"

Frisk tried desperately to explain, but continued trying to inhale, choking on their sore throat. Toriel had jumped out of bed and was next to Sans in what seemed the blink of an eye. "Oh, my poor child! Sans, what can we do?"

Sans, panicking, tried to think. "Breathing, ummm, inhaler! Doesn't the doctor keep one in our bathroom for when she comes over?" Frisk nodded, coughed, and clenched their fists as they tried to force their lungs to open and let air in. Toriel placed her arms around Frisk to hold them upright, and Sans ran to the bathroom. He flung the mirror cabinet door open, and saw a box with the end of the inhaler sticking out. He brought it up and handed it to Frisk, without realizing any of them probably didn't know how to use it. Frisks instincts kicked in, remembering seeing Alphys use it before, and gasped openly and loudly, finally able to inhale and exhale without struggle. The two worried monsters at Frisk's bedside clung to them, hoping to hear that they were all right.

"That's… a little better." And a sigh of relief filled the room.

"What happened, my child? Why couldn't you breathe?"

Frisk, exhausted and shaken, slumped into her arms. She held them up as she grabbed another pillow to prop up the child. "My coughing got really bad, and I took a shower to see if it would help, but it just got really swelled and sore." Frisk paused, breathing heavily and trembling, "I had a big cough, and then I just couldn't inhale." A tear fell down from one of their eyes as their shut them tight. "Thank you, Sans, I didn't know what to do, I didn't know we had an inhaler here."

"Lucky we had it too…"

The weekend flew by. Frisk stayed in bed mostly, getting checked on by Toriel and Sans, and even Dr. Alphys came to visit. "I'm not a medical doctor, you know," to which Toriel nodded. "I know, but it's nice to have an outside opinion on the matter. Especially an academic one!"

Alphys blushed a little, and continued, "well, it _is_ a good thing I left this inhaler here, I think it helped a lot. Don't use it too often, it stops helping if used too much too fast. It's also not powerful, since lizards don't need as much as humans, but I think it's a perfect dosage for Frisk, since they're a kid." She checked the counter on the back of the inhaler. "There is still plenty of juice in it too, but Frisk is usually pretty healthy, this is pretty unusual."

"What do you mean?" said Sans, who was walking in with tea for Alphys.

"Well, this sounds like it's probably bronchitis, from the way Frisk describes it, but it shouldn't get that bad, Frisk is a healthy kid. This must be a pretty bad case."

Toriel kissed Frisk's head, "we'll take good care of you sweetie."

Tuesday morning, Frisk was worse than before. Sleeping only 20 minutes at a time, their coughing became an exhausting nuisance. Frisk tried some medication that a medical human doctor provided, but it only helped a little. Sans came in when the coughing became particularly bad just to be safe. Frisk felt terrible, not wanting to cause too much concern.

"You're sick, it's why I'm here. You holler or cough, I'll come check on ya."

Frisk nodded, finally feeling comfortable enough to get some sleep.

Sans was thrilled when an hour passed with no coughing, even checking the bedroom for noise; only hearing breathing. Frisk had to be continuously sitting up, even when sleeping, and Sans felt bad it had been so hard for the kid to get some shut eye. He had finished some chores, and turned on the television for a little bit. About half way into the program, he heard a noise come from upstairs, and then Frisk's door opening violently. Frisk, nearly tripping down the stairs, coughing and choking, ran to the bathroom. Before Sans could say anything, he heard the child puke in the toilet, and then gasp for breath. Sans rushed in, and knelt down to try and help. It was another minute or so before the coughing subsided; Sans stayed with Frisk instead of getting the inhaler in fear of leaving the child alone. Frisk breathed audibly, seemingly gasping for every breath. Tears of exhaustion and pain flooded Frisk's eyes, pouring off their pale face. Sans wiped the remaining puke from the kid's chin, and wrapped them in a clean blanket from the closet.

"Let's get you to the couch, so you're closer to the bathroom." Frisk nodded and was lifted up and guided gingerly to the soft loveseat. Sans went upstairs to get the inhaler, and came back down to a very blank-faced patient on the couch. "I'm so tired Sans… I don't know how much more I can handle. It takes longer and longer to catch my breath… it feels like I'm drowning."

Sans sighed, "I'm not even sure what to do anymore. Nothing seems to be working to get you better. Maybe that doctor should increase your medicine."

Frisk, nodded, barely paying attention to what Sans had said. "Try to get some rest, I'll make soup." The child continued crying softly until the skeleton brought out the soup, a bowl for each of them. "It's still a little hot, give it a second."

A very course cough escaped Frisk's mouth, as they sat up a little more to have some soup. They took a bite, closed their eyes, and savored the taste. Sans had made the seasonings a little stronger so Frisk could taste it better. Frisk leaned their head to rest on Sans's shoulder, "Thank you", they said weakly.

Then, suddenly, Frisk sat upright, and twitched violently, blinking in sync with several more head twitches. Sans looked at them, as Frisk placed a hand on their head. Another twitch, and the hand scrunched into a fist, pulling on the hair a little, and then whacked their own head a couple times.

"Hey, what's…?" Sans's face dropped. Frisk's eyes flickered between their natural brown, a sickeningly vibrant red and complete black. "Uhhh… kid…?"

Soon, Frisk began coughing once more. Violently, their whole body convulsed with each enormous cough. They threw the blankets off and purposefully lunged for the floor as the coughing continued. Then, their eyes rolling backwards, their skin flushed nearly pure white and fell backwards onto the carpeted floor.

"Damnit, kid, wake up!" Sans yelled, reaching for the blanket and slid it under the kid's head as the child helplessly convulsed on the floor. After a few seconds, Frisk coughed violently, unable to breathe again, choked up out of their lungs a small black lump, and then fell over. Sans, immensely freaked out, picked up the small lump, it looked like a large, dusty seed. He put it in his pocket and looked down upon the kid, caught in a cold sweat barely holding on to breathing let alone consciousness. Sans picked them up, placing them on the couch while dialing Dr. Alphys, asking her to come immediately.

After about 10 minutes, a very defeated looking Sans answered the door to a nervous yellow lizard and her girlfriend.

"We came as soon as you called," Undyne explained.

Sans held the small black object up, and she took a step back. "That came out of their…" San nodded before she finished.

"That's… quite bad. How would that get in there?"

"What is it?" the skeleton asked, very insistently.

"Well it looks like a flower pod, but…"

Undyne and Sans glared at Alphys terrified, and then they all looked at Frisk who was sleeping very deeply on the couch.

"Gee, I haven't seen Frisk since Sunday, the bags under their eyes are so dark."

The three of them quietly passed through the living room to talk in the kitchen. "Have you told Toriel, yet?" Undyne asked.

Sans shook his head, "No," he exhaled deeply, "I'm afraid of what she'll say, she loves that kid more than her own self."

"If things get better progressively, I think we should wait and tell the both of them what happened in about a week," Alphys said. "I know that seems like a long time, but if Frisk knew I doubt they would rest easy."

They heard a small, startled gasp come from the living room, and then a very weak voice crying out "Sans?" A small sob, and then again, "Saaaaaans..?"

Sans came out, leaving the other two in the kitchen, "hey, you're awake." Looking into the small child's barely awake eyes. "What's up?"

"I…I'm so scared… what happened? Why do my muscles hurt?"

"You had a bad coughing spell and passed out." He tried to word it carefully, not wanting to lie but also reluctant to explain everything. "Alphys and Undyne and I were in the kitchen, want some company?"

"I want mom." There face scrunched up as they cried helplessly, sobbing at nearly a yelling volume.

"Shhhh, hey, I'll call her and have her come home. I know she'll come straight home for you."

Indeed she did, and in very little time Toriel returned home to find Sans with Frisk's faced buried in a pillow. "Oh, dear Frisk, what can I do?" She kneeled down next to the child, and was allowed to lift the pillow away from their face, burning with tears.

She slid herself on the loveseat and raised the child onto her lap, and the two of them hugged each other tightly. The three of them feel asleep on the couch.

Frisk awoke part way through the night, mostly out of habit from coughing upon waking up. They made sure to cover their adoptive mother with a blanket before going to the bathroom.

They flicked the light switch, and looked in the mirror. Dark circles starting to become bags under their eyes, pale as a ghost, and even their usually chubby cheeks had gotten thinner. They reached into the cabinet to take their overdue medication, and scooped some water from the faucet into their hand to wash it down. Taking a big sigh, Frisk turned the light back off, and started out of the bathroom, but jumped backwards when they saw Sans standing outside the door.

"Hey there, pal, feeling all right?"

Frisk, still catching their breath from having the crap scared out of them, nodded, and smiled faintly. "I'll be fine, although I doubt I will get back to sleep now."

Sans, stared down at the floor, feeling guilty, "sorry…"

Frisk shook their head, and leaned in to hug the skeleton. "This just means you gotta stay up with me!" They said, beaming. Sans was relieved, this was the happiest the kid had seemed in a long while, let alone since getting sick. Sans agreed, and they climbed the stairs carefully trying to avoid waking up Toriel.

Once they had gotten up to Frisk's room, the child climbed onto the bed and wrapped the remaining blanket around themself, like a large cloak.

Sans stood in the doorway, hesitating, trying to decide whether or not to mention the events of the previous day. Frisk looked over, their smile fading. "Sans…? What's wr-"

"Can you remember any of it?" San interrupted, looking the child completely deadpan. "Can you recall anything about that last coughing fit you had?"

Frisk was scared, and they weren't even sure why. "I remember coughing, falling to the floor, and then everything went dark." They stared down at their own hands, now fiddling with the folds of the blanket. "My lungs felt awful, and my head was spinning violently. Before I blacked out, I remember feeling like something was ripped out of me." Frisk looked up at Sans, too terrified to even let the tears welling up to escape the edges of their eyelids.

Sans walked over, hands in his pockets, and pulled out his phone with had a picture on the screen. "You coughed this up…" Frisk furrowed their brows, confused. "Alphys says it's a massive seed pod. She currently has it for testing, but said it's the reason you had been so ill."

Frisk covered their mouth, stifling a scream, just breathing heavily. They backed away from Sans, up against the wall while still sitting on the bed. "Hey, calm down kid, it's gone now, it won't hurt you anymore."

Frisk's panic spiraled, both sobbing and shaking in utter fear. "Don't let it…don't let them hurt me…"

"Them?"

"F-flowey… Asri-Ariel… th….them…" the child stuttered through their fear.

Sans crawled up onto the bed, kneeling next to the trembling kid. "Hey, we got you, they won't ever-"

"PLEASE… they'll kill everyone…I don't want to lose you, or anyone. They don't CARE, Sans, they will keep killing and destroying and.." their ranting fading as Sans held them close, letting Frisk's head bury into his blue hoodie.

"Shhhhhh…. They aren't going to reach you. It'll be fine…" Sans let his inner powers become visible, his left eye turned bright blue. "They'll have to get through me first."


	2. Chapter 2

A/N – Thank you all for such a good response! It has been over 6 years since I've written any fanfic, and I'm extremely thrilled about the reception. The experiences are loosely based off of when I had bronchitis in the Fall (however I was prescribed the medication and inhaler).

The following morning, Frisk had been feeling much better. They slept through the night, and woke up surprisingly refreshed. Sans slept in late, falling asleep back on the couch with Toriel. All of them woke up pretty early, wanting to see Toriel off to work in the morning. Toriel had insisted that Frisk should take another sick day, just to be sure they were well enough to go back to school. Alphys had also asked for Sans to bring the kid over sometime during the day to get a X-ray. Although Alphys wasn't a doctor, she had all the necessary certifications and safety equipment.

Toriel left for work, leaving Sans and Frisk together on the couch enjoying some breakfast and tea. Frisk had a few small coughs, but nothing as bad as before. A little while after breakfast, the two started walking to Alphys's lab, which was a long walk across town. The walk started off fun, there was a pretty path through the park which was longer but more scenic. The two of them joked and talked for most of the walk, stopping every once in a while when Frisk saw a butterfly or something they thought was cute. It amused Sans, and made him thrilled to see the kid in such higher spirits.

As they walked, Frisk stopped, and turned to their left. They stayed there for a few seconds because Sans had realized they had stopped. "Hey kid, what'd you find?" He asked, smiling. When he was given no response, his smile dropped and he walked up to them slowly, realizing their eyes were closed. "Uhhh, hey kid, feeling okay?" They gripped their head and dropped to their knees. Eyes now wide open and completely bloodshot. "Stop…" they said.

Sans stopped in his tracks. "Kid?" He noticed their eyes burning red, and stepped back.

"Please don't say that… why… please? No…." Sans stood confused, not wanting to get involved if it would hurt Frisk. They dropped their hands onto their knees, and looked up at Sans. Their red eyes started to fade back to brown.

"Can…can you stand?" He wasn't sure what else to do or say.

"Probably, let me try," they steadied themselves slowly, their knees wobbling a little as they finally stood. Their knees were scraped from the pavement, and something had definitely shaken them up.

"Good," he sighed for a second. "I'm not saying we ignore what just happened…but let's wait until we reach the lab to say anything. Deal?"

Frisk, now uncharacteristically quiet compared to before, nodded and caught up with Sans's pace until they finally reached the lab. When they did, the kid took a deep breath and Sans noticed them concentrating on something. They were then interrupted by the sound of footsteps approaching.

"Hey, y-you're early! But, I've had everything set up s-so… are you ready, kid?" Alphys asked nervously, she was honestly concerned about what they might find.

Frisk nodded, and Sans sat down by the door. "I'll be here when you get back, it won't take long." The two exited through a door, and the moment it closed, Sans collapsed a little where he sat. This was bad, in fact it was worse. He began to nod off, just collected his thoughts.

Frisk had changed into a medical robe, stood in front of the scanner, changed positions when Alphys requested. Their ribs still hurt from being ill, but they still managed to hold their arms up without fail through the entire thing. "I think we are all set! Go change and I'll come out with the results in a bit. I haven't heard you cough once since you got here, so that's good!" Frisk nodded, smiling a little from Alphys's optimism, and then changed back into their favorite sweater and zipped up their pants.

Frisk poked their head out into the front room, and saw Sans sitting on the floor. He looked exhausted, but still sat up to greet them, and Frisk's heart dropped.

"How'd it go?" he inquired, his voice a little deep from his nap.

"I think it went okay, Alphys seems hopeful. I hope she's right." Frisk smiled and pulled Sans up off the floor, and the two of them took seats on the cough a few paces away. They both wanted to talk about the walk over, but neither one could think of how to begin.

Alphys emerged with a mess of papers in her hands. "Hey guys, g-give me a moment," she said, organizing the various files and print-outs before sitting down across from them. "Okay… so.. umm… I'm not really sure how to explain this…"

Her expression was enough to make Sans anxiously suspicious that something was still wrong with Frisk. Very wrong. "Here, why don't we go into the other room, and I'll help you find the right words." Alphys nodded, and the two of them went into the other room, leaving Frisk with their thoughts.

 _You know what is going on, don't you? You knew I wouldn't give up so easily, didn't you? I'm not just going to kill them._

 _I'm going to make YOU do it._

"So, at some point when Frisk was facing Chara and Asriel, I think they planted these seeds to hold their two souls until they were strong enough to come back. Since none of us really remember what happened between them, and Frisk blacked out before we found them… I think that's when it happened."

"So you think Chara made them get sick?" Sans inquired, his bones trembled at the thought of facing those two ever again.

"On the contrary, I think it was Asriel. I think he was trying to back out of the plan, which I think is why-"

"Why Frisk coughed one of the seeds up." Alphys nodded. "So, if we can get the other seed out and keep them away from a host body…"

"Then we can keep them from coming back!" Alphys paused, "But…"

"But?"

"I don't know if we'll be able to get it out or not. Surgery would be difficult..." Alphys started looking through her files nervously, trying to avoid seeing the anguish in Sans's face.

"What if…we try an experiment?" he asked, patiently.

Alphys looked up, took a moment to think, and then looked at Sans. "What are you suggesting?"

"If I focus hard enough, and try to force the seed out with my magic…" he looked at Alphys, his eyes desperate for her approval.

Alphys stared off, considering the idea. "Maybe… we would have to make sure Frisk is either comfortable or unconscious."

"All right, let's try it then." Sans started walking back to the lobby.

"RIGHT NOW?" Alphys followed behind.

When they returned out to the lobby, Frisk was curled up on the couch, holding their knees up to their chest. They quickly wiped the tears from their face, and looked up at their approaching friends. "Heya, kid. We're gonna try something out, can you turn around for a second?" Frisk nodded, confusedly, and turned away.

Sans had recalled from Alphys's notes that the remaining seed was in the left lung, and his left eye started to emit a blue flame as he started to prepare his power. He focused hard, picturing the seed, and raised his hand to try and guide it out of the organ. Frisk flinched in pain, crying out audibly. "It's all right, just keep facing that way." Sans tried again, and saw Frisk grabbed their ribs and whimpered.

"Sans, stop!" Alphys cried. He kept going, trying desperately to pull the seed out, but he could feel it barely budging. He stopped for a moment, trying to decide what to do next. "Sans, what we you thinking?"

Frisk turned around, their eyes closed. "Oh Sans…" Their eyes shot open, their usual deep-brown eyes were now a sharp red color. "What _were_ you thinking?"

Sans and Alphys froze in horror. "Stop that! You leave them alone!" Sans yelled, using his power to toss the child across the room.

"Sans, don't!" Alphys cried out.

They stood up, unfazed by their impact with the wall, and tilted their neck to the side. "Oh… so that's how it is." They started running toward Sans, only to be pushed away once more as Sans raised his arm, and held it up to keep them pinned against the wall.


	3. Chapter 3

A/N – Slowly but surely correcting some spelling/grammar in the first two chapters, I'll keep going with corrections through the week.

Also been dying to write some Adult!Frisk/Sans, or I can do more stuff like this. (or both) Suggestions in comments, I'm open to requests for one-shots and such.

"Now you just stay right there, and we're going to have a little talk, you and I…" Sans was now just a couple of feet away from where he had pinned Frisk up against the wall. But right now, it wasn't Frisk… it was Chara. Alphys was several yards behind him, anticipating the worse.

"Oh, that's no way to greet an old friend, Sans! After all, it's so much more interesting to play with you." They giggled demonically. "I knew when Asriel was beginning to fear me, I needed a new friend to play with. Someone who understood rage, someone with a sick sense of humor…" Sans's grimace was accompanied by a loud snarl. "I needed one of _dad's_ scientists who didn't mind letting me help with your disgusting experiments…" Chara snickered, enjoying the immense fiery rage that was burning inside Sans.

Suddenly, the child's eyes began flickering back to brown. "Stop that!" Sans snapped out of his fury enough to remember what he was trying to do in the first place. He once again tried to pull the seed pod out of Frisk's lung, only causing them to grimace again, and their eyes flashed back to red. "You IDIOT. Once Asriel started his little stunt, didn't you think I would take precautions? I'm already rooted deep in their lung, reaching closer and closer to that soul of theirs."

Sans yelled, trying once more to rip Chara out, but to no avail. He panted heavily as their eyes faded once again back to brown, and he caught Frisk as he released them from his magic grip. They were shaking, Sans couldn't tell if from fear or pain or both. He let them catch their breath, before he broke the silence in the room. "Kid… did I hurt you?"

Frisk shook their head, lying. They were sore from being whipped around, but was more hurt that Sans had never told them about his previous friendship with Chara. Alphys walked over slowly, and knelt down to get a better look at Frisk. "You have some br-bruising, but thankfully you look fine otherwise." Sans lifted Frisk onto the couch to let them rest, and then finally looked at Alphys. She had been watching Sans's every move, scowling, "Sans, what were you thinking? You could've really hurt them! That might have been Chara in there, but Frisk…"

Sans shut his eyes tight, "I know, I know, I'm sorry. I wasn't ready for that… I wasn't…"

"And what about this whole scientist thing? There are traces in a lot of the lab's notes about the former Royal Scientist and their assistants, but no names. But the experiments they did… the things they did to souls, human and monster... When were you going to tell us?" Alphys was fuming, more so than when she would rant about Mew Mew Kissy Cutie 2.

"NEVER, OKAY? I never wanted any of you to know about that! I quit for several reasons, I couldn't stand it anymore! I confessed to the king and queen everything we had been doing, and when the Royal Scientist found out, he closed down the lab and made everyone forget, except me. They forgot him, they forgot I worked there, everything." His eyes disappeared, leaving a black void in his eye sockets. "But I remember… I remember everything, and I wish I couldn't." His eyes slowly returned, faded blue tears dripping out of them. "But apparently, THEY remember too…"

Alphys stared, mortified. "That… makes sense. It probably only affected monsters, didn't it?" She received no response from Sans, who had shut his eyes tightly again. "Sans… I'm sorry…" She recalled back to the endless books of notes in the basement of the lab. Tortured souls, human and monster alike, were experimented on time and time again, trying to unlock the power they contained.

Sans felt a tug on his hoodie, and turned around to see Frisk with an extremely worried look on their face. "It's gonna be okay, Sans." Sans felt completely defeated; he dropped to his knees, accepted the hug Frisk offered with their open arms. After a minute, he stood back up.

"I need to call Tori… Alphys, are there any human doctors who could do the surgery that you trust?" Sans pulled out his phone to leave a message since he knew she was working.

"I-uhhhh… I may know one. I'll see if we can set something up for tomorrow." She said, grabbing a small address book on one of her bookshelves. "Do… do you think Toriel would mind if we kept Frisk here overnight?"

Sans paused, he'd have a lot of explaining to do. "I… I think she'll be fine with it? I'll ask. Under the circumstances, I think she'll understand."

They both made their calls, and everything was in order. Undyne was coming later to hang out with Alphys, so they decided to just invite everybody over to the lab for dinner: Papyrus, Toriel, even Asgore. Toriel brought over some extra clothes and a blanket for Frisk to sleep over at the lab, asking Alphys endless questions about the procedure and the doctor. They played board games, watched Mettaton's show, and then all except Alphys, Frisk, Undyne and Sans had gone home. Toriel would've stayed, but she was so worried she didn't want to overreact and cause unnecessary stress on anyone.

Frisk fell asleep leaning up against Sans, who was still watching television until he also fell asleep.

The next thing he knew, he was being shaken awake by Alphys. "S-SANS! OH JEEZ, SANS, FRISK IS G-GONE." The sleepy-eyed skeleton woke up immediately upon hearing this.

"Fuck… but where would they-"

"I checked m-my cameras, they got up and left in the middle of the n-night. Just… out the front door! Oh man, Sans, what d-do we do?"

"I'm going out to look. Call everyone" Sans ran out of the lab frantically, called Frisk's name continuously.

They all searched around the area; every part of town, behind every tree in the nearby forest. They searched for two days, until they all met at Toriel's to create a strategy. They spent an hour debating what to do next, all except Sans. He was silent. Once the yelling escalated loudly enough and he couldn't take the pressure anymore, he finally spoke. "HEY!"

The room went silent, all eyes on Sans. "What if… they went back…"

"Back where? We know they aren't at the lab!" Undyne said roughly.

Sans looked at Toriel, who knew what he meant. "He's right… it's the only place we haven't looked. I think… I think we have all been secretly hoping they wouldn't have gone there."

It clicked in Alphys's head too. "Oh no… no you're right…"

Undyne looked at her girlfriend, confused. "What? Where?!"

"Back… to the Underground?" Papyrus asked, nervously. "But why?"

Toriel sighed. "Sans, you can get there faster than any of us. I know you can, with your shortcuts. Please…" she sniffed. "Please go find them, we are right behind you."

Sans nodded and in an instant he was gone. He flashed from shortcut to shortcut quickly until he reached the entrance. His eye now flaming its bright cyan hue, he started into the large cavernous entrance. It was dark for a long time, until he had crossed through, and into the abandoned throne room. He saw one of Frisk's sneakers, and then bolted ahead. He knew exactly where they were. He walked into the large, grand hallway adorned by stained glass and columns. At the end of the hallway, he could see Frisk lying on the cold floor. He was about to run towards them, when he remembered who he was really there to deal with.

"All right, Chara… I'm here. Just you and me, like old time's sake." He took a step forward, noticing the body stir a little. "That's right… just us. The birds are singing, flowers and blooming, and well…" Suddenly, the child sat up with burning red eyes, just as Sans had predicted. "Well, you know the rest.

Chara screamed loudly, which was painfully amplified by the hall's acoustics. Sans stood his ground, dodging the swipes and punches thrown at him. "Gee, kid, you just don't give up, do you?" He reached his arm out, and they went flying backwards. He knew exactly what to do. He let them advance again and when they got close enough, he placed his hands on their shoulders, not letting them budge.

"You IDIOT…" Chara said, before drawing out a knife and shoving it into her ribcage. He winced but didn't move from where he stood. He phased he hands through their shoulders. "What…what are you doing? STOP THAT." In the blink of an eye, he tore Chara's soul out of Frisk's body, which fell limp to the floor. Before him, stood Chara in a cloud of black smoke, looking at him angrily. "I still won, you fool. I've held Frisk down here for two days, trying to kill them and take their body. But their damn determination… their fucking love for ALL YOU MORONS! They kept holding on, they wouldn't give up. But now they're on the edge of death, and so are you. Once you both kick it, I'll take BOTH of your souls! It's only a matter of ti-" Frisk was standing behind Chara, their hand driven through their chest, Chara's soul in their hand. Reaching another hand through, despite Chara's screaming and thrashing, Frisk held the soul tightly in their cupped hands, staying absolutely still. Seeing what they were trying to do, Sans summoned a blast of blue light which ripped Chara's soul apart, and the smoky mass dissipated. Since Frisk hadn't moved, they remained unhurt by the attack.

They both coughed, choking on the disgusting evaporating soul. Once it had cleared, Frisk gasped, "Sans! You're hurt!"

Sans, forgetting his injury looked down. "Oh yeah…huh…"He collapsed to his knees.

Frisk approached Sans, their own body weak from exhaustion. "Sans? What do we do?!" Everything started catching up to them, the pain, the fear, and they began crying profusely.

Sans's usual smiled dropped, "hey now, kid, no need to worry. I'm gonna have to ask you to do something for me." He knew this would be difficult to ask of Frisk, but they looked at him, eager to do anything. "There is some candy in my jacket. Unwrap it and put it in my mouth. Then…" he sighed, gathering his strength, "I'm gonna need you to pull this knife out." He knew he would need to be fast to pull this off, but was comforted by Frisk's nod.

They got the candy out, a small piece of taffy, and placed it between Sans's teeth. "Are you.. ready?" Sans took a deep breath and nodded. Frisk quickly pulled the knife out, and then placed their hands over the hole in the t-shirt. Sans swallowed the candy whole, and closed his eyes, pulling Frisk in for an embrace. They had gotten so thin in two days, they must've been in so much pain. Frisk continued sobbing, and he held them even closer.

"Hey, hey, it's all right. I'm all good now. My bones are a little rattled but, hey, it takes a lot more than that to kill me." Frisk giggled a little, and then leaned backwards to see for themself. Unfortunately, this also meant Sans would see how much damage was done to them, and it made him cover his mouth.

Besides being malnourished and dehydrated, their eyes were dark and swollen from a lack of sleep. Their hands and fingers had bruises and scrapes from handling Chara's soul directly. But still, the only pain in their eyes was from seeing Sans hurt, and it broke his heart.

"We gotta get you outta here, kiddo." Without protest, Frisk let themself be carried through the dark passages and tunnels out of the Underground.

It was finally over… they were gone.


	4. Chapter 4

A/N –I'm so happy that so many people have favorited, followed and reviewed! It means a lot to me! I'll be back with more, and I'm open to suggestions/commissions/etc.

I have another fluffy SansxFrisk story in the works, first chapter is up, so please check it out if you are interested!

(A little bit of cursing in this one, you have been warned)

 _Epilogue_

"Oh my goodness! Frisk! Sans!" Toriel called out, running towards them. The group of concerned monsters were about a hundred feet from where they saw a very exhausted Sans carrying Frisk, who was deeply asleep.

"Hey Tori… I found the kid. They are a bit shaken up, so I'll just keep carrying them until we get home."

"Why aren't you using your powers to teleport back? You've been gone for so long!" Alphys, who had now caught up with Toriel, inquired.

"Just a bit low on the magic batteries, is all. It's been a nice walk." He couldn't lie, it was relaxing to walk through the empty Underground, like walking through faded memories.

"BROTHER! I SEE YOU HAVE GOTTEN A HOLE IN YOUR SHIRT! I WILL MEND IT WHEN WE GET HOME! I'M SO GLAD YOU AND THE HUMAN ARE ALL RIGHT!" Papyrus rushed to his brother's side, and gave him a gentle hug so he wouldn't wake frisk.

"Since you won't put the kid down, why don't I carry you BOTH?!" Undyne asked, beaming her toothy grin.

"Really, everyone… it's okay. Kid here saved my life, and vice versa, but it won't be that long of a walk now."

They had all reached Toriel's house, warm and tidy, and settled in to get together for old time's sake. Frisk lay sleeping in their room upstairs, and Sans tried desperately to not fall asleep on the couch while everyone was over.

"So, Sans, there is s-still the issue of what to do with the remaining seed pod." Alphys asked the half-asleep skeleton.

Sans thought about it for a moment, "Hey Tori, could you come here?"

"I'm just getting the pie out of the oven, give me one minute." She called back.

S-sans, are you sure that's-"

"Asriel _was_ her child, it's her decision what should be done with his soul. Since we can't communicate with him, she should really make the decision." Alphys nodded in agreement with Sans's suggestion.

"Hey kid! You're awake!" Undyne called up the stairs. Descending down was a very exhausted, thin looking Frisk. Except for Sans, no one else had gotten a good look at the damage that was done. Now that they'd had some sleep, the dark circles under their eyes had gotten lighter. Frisk waved at Undyne, carefully climbing down, once they reached the bottom, they made direct eye contact with Sans. The two of them stared at each other for a moment.

 _Sans pulled the kid up onto his back. "Hold on kid, I'll try and make sure it's not too bumpy." He could feel Frisk nod their head, as they gripped Sans's upper chest tightly. Sans, tried to teleport, but only went a foot or two. "Damn…" he tried again; a little more progress, but Sans found himself already exhausted. "Kid, can I put you down for a moment?" After getting another small nod, he gently set the kid down, and tried teleporting again. He only ended up another few feet from where Frisk was sitting. "DAMNIT!" he dropped to his knees, pounding his fists onto the ground._

 _"Sans?"_

 _After a silent heavy breaths, Sans opened his eyes, he had made cracks in the stone floor. He furrowed his brows, surprised by his own strength, then looked over at Frisk. The child was deeply terrified; they were crouched over with their hands over their ears. Sans could hear them letting a few sobs escape, and he looked around him. The cracks he had made ran farther than he originally thought, and he hands had a familiar bright blue glow, which soon thereafter faded. He got up, and carefully navigated around some of the deeper cracks back to Frisk._

 _He knelt down, and gently removed their hands from covering their ears, and was then met with a pair of soft brown eyes. "Hey kid… I'm sorry for frightening you. I'm not quite good at this hero thing, ya know?" Frisk raised a hand up to his chest, his soul pulsed. "I couldn't protect you, I have nothing left for you to eat, and now you're terrified. It'll take us hours to get back to the others." Frisk softly rested their hand on his sternum, just over his soul, and it pulsed again. And again._

 _"I… I don't care how long it takes." They finally said. "I just don't want to see you get hurt. I can walk, it's okay…" Sans heaved a heavy sigh, even if Frisk could walk, it wouldn't last long. But he had to let them try, he needed to recover his own strength._

 _They both started walking, Sans tried to go slowly so the kid wouldn't worry about keeping up with his pace. They got to the throne room, the one well-kept garden in disarray and overgrown. They hadn't gone very far, but Frisk was already panting and out of breath, they pushed themself too far._

 _"Hey, doing great kid, almost there." Sans tried to encourage them, but he knew that wouldn't help physically._

 _"I'm sorry…" Frisk said, hands on their knees, trying to catch their breath. " I can't…" they panted harder, trying hard not to pass out. "I can't sta-" They fell over, Sans catching them inches before hitting the ground._

 _"Hey, kid, I got you… it's all right." He didn't get a response. "Kid, come on, don't give up on me, we're almost out. I need you to stay awake." He held their head, and gently sat them up on the ground. He grunted, pulling them onto his back, which proved much more difficult when they couldn't lift themself up. He noticed he had regained a bit more energy, and started walking into the long, dark hallway towards freedom. "Well, can't say you didn't try… but you can't push yourself like that again."_

 _He heard a whimper come from Frisk, "I'm sorry…" because they went silent again._

"How are you feeling, my child?" Toriel asked sweetly.

"Very hungry…" Frisk said quietly.

"I just pulled a pie out of the oven, but I think you should have something with a little more protein and vitamins. Perhaps you would like some soup?" Frisk nodded.

"I'll make it Tori, you relax." Sans offered, to the surprise of everyone in the room.

"BUT BROTHER! YOU ARE BARELY AWAKE YOURSELF!" Papyrus said, "AND, YOU DON'T COOK!"

"I can make soup. C'mon kid, why don't you join me?" Sans got up from his spot on the couch, and nudged Alphys why gesturing towards Toriel.

"Oh, right… um… Toriel… we need to t-talk…" Alphys said, motioning for Toriel to take Sans's seat.

The skeleton and Frisk went into the kitchen, both exhausted, and probably the last two people in the building that should be cooking. Sans opened the fridge, pulled out some vegetables, and started dicing them up. "Can you grab a pot and fill it half-way with water?" Sans asked awkwardly. There was so much he wanted to say, but this was more important at the moment.

Frisk nodded, pulling a shiny pot from one of the cabinets, and set it down in the sink to fill. They filled it part way, and then placed it on the stove, turning the dial to turn on the burner.

"Are you okay, Sans?" Frisk asked, tugging at his hoodie. "You look really tired."

"Have you looked in the mirror kid?" San replied, shrugging off the comment. Frisk was taken aback. "There is such a thing as being a little too selfless, kid. I'm fine, _you_ really gotta eat something, this soup is gonna take a while."

Frisk grabbed one of the carrots that Sans hadn't yet started chopping, and munched on it while watching the pot of water on the stove.

Sans sighed, "Sorry kid, I didn't mean to snap… yeah, I'm pretty tired, I guess."

Frisk had stopped munching on their carrot, and walking toward Sans. He put down the knife, and looked at them. "What's up, kid?"

"You…thank you." Frisk plunged face first and hugged Sans tightly. Sans returned the hug, smiling.


End file.
